1. Field of the Invention
The invention relates to the field of power systems. More particularly, the present invention relates to a power system having multiple channels and means for balancing channel currents.
2. Discussion of the Related Art
Isolated AC-to-DC power systems with active power factor correction (APFC) have been used in several applications involving active power factor correction for drawing sinusoidal currents from utility grids or input AC power sources, and regulation of DC output voltages being isolated from the grid or the input power sources. Without active current sharing, parallel connection of these identical power systems, respectively at their AC inputs and DC outputs, is not feasible as a result of far from uniform current-sharing among the paralleled power channels.
When parallel-connected, only one or a few power channels have a dominant power contribution while the remaining power channels are idle or make small contributions to the common output load. In many cases, the over-subscribed power channels have increased unreliability and shortened lifetimes due to, inter alfa, persistent thermal overstresses.
The parallel-connection disability discourages the application of the existing low-power AC-to-DC converter systems for large loads having demands exceeding the power rating of individual AC-to-DC power systems. Consequently, conventionally designed AC-to-DC power systems are not typically ganged together to supply large loads. Instead, a newly designed stand-alone APFC and converter power stage suited to the higher power demand is the typical solution. In other words, incremental power expansion is not feasible with conventional AC-to-DC power systems supplying a common load that grows to exceed the capacity of the original power system.